1. Technical Field
This disclosure relates to an image forming apparatus.
2. Description of the Related Art
Image forming apparatuses form an image using developer such as toner or ink. An amount of remaining developer is detected with a sensor or estimated by, for example, counting the number of image forming jobs or calculating a total number of recorded pixels of image data used in image forming, or a combination thereof. When remaining developer becomes low, a display unit indicates that a bottle or a container of the developer needs replacement. When the developer remaining amount drops to zero, the image forming apparatus does not perform image forming in response to an instruction to form an image.
Japanese Patent Application Laid-open No. 2002-278249 discloses a conventional technology in which a toner consumption estimated by counting density values of pixels of an image to be formed. A toner remaining amount is updated to a value obtained by subtracting the toner consumption from an initial toner amount, which is an amount of toner in a newly-replaced toner cartridge.
Japanese Patent Application Laid-open No. 2006-243492 discloses a conventional technology having a plurality of image forming modes for suppressing developer consumption by correcting a density of image data, in which remaining service life of an image carrier is detected. The image density is controlled by adjusting a condition for an image forming process so that an amount of remaining developer becomes zero simultaneously with the service life of the image carrier expires.
Japanese Patent Application Laid-open No. H10-319789 discloses a conventional technology in which an image forming apparatus indicates that remaining toner is low on an operating panel when remaining toner becomes low. When a toner-saving mode is selected by a user, the image forming apparatus changes an output power of laser beam that forms a latent image or a bias current value of a primary charger, thereby decreasing image density.
Japanese Patent Application Laid-open No. 2005-277747 discloses a conventional technology in which a toner consumption is maintained constant over a predetermined period by estimating and adjusting a toner amount to be consumed for an image to be formed for leveling consumption cycles of a plurality of toner cartridges. For example, a density adjusting unit adjusts density values of pixels of image data to be printed so that a target value of toner is consumed in a predetermined period.
Japanese Patent Application Laid-open No. 2006-308854 discloses a conventional technology in which an estimated number of sheets required to print images of a current job is derived when a developer remaining amount decreases to a predetermined level. When the estimated number of sheets is greater than image-formable sheets, which is the number of sheets that can be printed with the remaining amount of the developer, a plurality of image forming modes is displayed each suppressing the developer consumption so that a user can select one of the image forming modes.
However, the conventional technology described in Japanese Patent Application Laid-open No. 2002-278249 is disadvantageous in that even when the toner becomes empty, the image forming apparatus prompts only replacement of a toner cartridge. Therefore, when image printing is attempted after issuance of an alarm, the toner can fall short during a course of printing, causing a print job thereof to be suspended and decreasing productivity. The conventional technology described in Japanese Patent Application Laid-open No. 2006-243492 is similarly disadvantageous in that toner can fall short during a course of image printing or a service life of a image carrier can expire, thereby causing a print job thereof to be suspended and decreasing productivity. The toner-saving mode described in Japanese Patent Application Laid-open No. H10-319789 allows to increase the number of image-formable sheets; however, toner can fall short during a course of a print job, resulting in suspension of the print job, which decreases productivity. The conventional technology described in Japanese Patent Application Laid-open No. 2005-277747 is similarly disadvantageous in that when a print job is carried out with a low level of remaining toner, it is likely that a toner cartridge needs to be replaced during a course of a print job. This can result in a decrease in productivity. Suspending a print job and causing downtime during urgent printing of a document can cause let business opportunities slip away. The conventional technology described in Japanese Patent Application Laid-open No. 2006-308854 is disadvantageous in that when image forming of a large number of images is started with the developer remaining amount higher than the predetermined level, the image forming mode that suppresses the developer consumption is not set in. Therefore, it is likely that the toner cartridge needs to be replaced during a course of an image forming job.